KR100866819B1 - Method for recycling pet bottle - Google Patents

Abstract

PET was recovered from the used PET bottle by depolymerization in EG and transesterification in MeOH. Consistent process for producing polymers.

Description

Recycling method of PET bottle {METHOD FOR RECYCLING PET BOTTLE}

The present invention relates to a method for obtaining a PET bottle polymer again from a resin bottle waste containing polyethylene terephthalate (hereinafter abbreviated as PET) as a main component, and more particularly, containing PET as a main component and After pretreatment such as crushing, washing, and removing foreign matters, the resin bottle waste containing different components is subjected to chemical reaction treatment to recover high-purity dimethyl terephthalate (hereinafter abbreviated as DMT) as an active ingredient. The reaction relates to a method of obtaining terephthalic acid (hereinafter abbreviated as TA) and further obtaining a PET polymer for PET bottles.

Polyalkylene terephthalate, especially PET, is produced and used in large quantities in food fields such as living materials such as fibers, films, resins, beverages and carbonated beverages, etc. because of its excellent chemical stability.

However, the disposal of wastes of fiber, film, resin products and out-of-standard PET, which are generated in large quantities with the increase of production and usage amount, is a big social problem. Thus, material recycling, chemical recycling, thermal recycling, etc. Various proposals regarding the recycling method have been made.                 

On the other hand, among the wastes, even though the disposal of PET bottles is becoming more serious due to its large volume, the recycling method is material recycling, in which only the recycled PET bottle is melted and re-fiberized. It is not performed, and when melt-molding simply, it is impossible to use it again as a PET bottle because of the fall of the physical property.

In addition, the refilling method for cleaning and refilling the PET bottle is not a permanent measure such as burden of recovery cost, safety and hygiene point of view, limit on reuse recovery, and eventually disposal. . PET bottle residues also include polystyrene (hereinafter abbreviated as PS) derived from components of PET bottle products such as labels, shrink films, base cups and caps, and polypropylene (hereinafter abbreviated as PP). Foreign plastics such as polyethylene (hereinafter abbreviated as PE), polyvinyl chloride (hereinafter abbreviated as PVC) and polyolefin resins such as polyolefin resins, The aluminum derived from a cap, an aluminum can, the iron derived from a steel can, an adhesive agent, a pigment, dye, etc. may be mixed.

It is difficult to avoid foreign material mixing even in the recovered PET bottle bales, and the PET polymer may be prepared using solvents such as water, methanol (hereinafter abbreviated as MeOH), and ethylene glycol (hereinafter abbreviated as EG). Also in chemical recycling, which is decomposed and reused into constituent monomers, the foreign material generates various decomposition gases (for example, hydrogen chloride gas, etc.) and various decomposition products (for example, lower hydrocarbons) during the heating operation and the reaction operation. In some cases, the mixture itself may significantly reduce the quality of the monomer (DMT) recovered by a chemical reaction. Or it may melt and solidify in a collection apparatus, and may damage an apparatus.

Examples of the chemical recycling include a method for obtaining TA by hydrolyzing a polyester waste in the presence of an alkali compound described in Japanese Patent Application Laid-Open No. 11-21374, for gas phase MeOH decomposition in MeOH described in US Pat. And the like to obtain DMT and EG.

However, since they all require high temperature reaction conditions of 200 ° C. or higher, the decomposition starts from 190 ° C. like PVC, and the degree of tolerance of incorporation of different polyester plastics from which the decomposed product causes deterioration of the final product quality. There is a problem of being very low.

In Japanese Unexamined Patent Publication No. 2000-169623, PET waste is decomposed by EG and the recovered bis-β-hydroxyethyl terephthalate (hereinafter abbreviated as BHET) is purified by a thin film evaporator. Subsequently, a process of melting and polycondensing BHET to obtain a PET polymer has been proposed, but in this case, there is also a process of imparting a thermal history of 200 ° C. or higher, and the thermally decomposed phase such as PVC has a low tolerance of mixing of plastics.

In other words, even in chemical recycling, impurities are allowed to be mixed more than material recycling, but impurities need to be removed almost completely in the pretreatment process. In addition, although it is extremely known that a PET polymer for bottles obtains an oligomer in a transesterification reaction or an esterification reaction with EG using DMT or TA as a starting material, and is subsequently obtained by a polycondensation reaction, the raw material DMT or TA is used. It is not possible to use the obtained PET polymer for PET bottles unless it is sufficiently refined with few impurities.

Due to such various restrictions, there is no method of recovering the active ingredient of the used PET bottle by the chemical recycling method and obtaining a PET polymer which can be used for the PET bottle again.

The object of the present invention is to solve the problems of the prior art, and to obtain a high purity monomer (DMT) without contamination even when impurities are mixed, and from the high purity DMT, a suitable PET polymer for PET bottles can be efficiently obtained. It is to propose a process that can be produced.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram for demonstrating the flow of a process typically showing one aspect of the PET bottle recycling method of this invention.

Best Mode for Carrying Out the Invention

In the present invention, a high-purity DMT as an active ingredient is recovered from a resin bottle waste containing PET as a main component and a component different from that, to obtain TA by a chemical reaction, and a PET polymer for PET bottles. The method of obtaining this is characterized by passing the resin bottle waste so that the process of following (1)-(17) may be included in order.

(1) A step of unpacking and unpacking the PET bottle packing bales collected and collected separately.

(2) A grinding step of forming a flake shape of 2 to 30 mm square after removing iron and aluminum from the unpacked PET bottle with a metal detector.

(3) Process of separating component polymer different from PET of label (thin film) which consists of PE, PS, PVC, etc. from flake shaped PET bottle piece by wind sorting.

(4) Washing foreign substances inside and outside of PET bottle pieces and / or contents residues in PET bottles with water, and removing sandstone and the like having a higher specific gravity than water and PET, and PE having a smaller specific gravity than water. Washing and gravity screening process which separates dissimilar plastics such as PP and PP.

(5) Depolymerization process which produces | generates BHET by putting collect | recovered PET flakes in EG containing PET depolymerization catalyst, and processing it at the temperature of 175-190 degreeC, and the pressure of 0.1-0.5 MPa.

(6) Solid-liquid separation process which removes the solid foreign material content which does not melt | dissolve in the said reaction solution.

(7) A BHET concentration step of distilling and concentrating a solution component that has passed the solid-liquid separation step.

(8) A transesterification and recrystallization step of subjecting the concentrated BHET to a transesterification reaction with a transesterification catalyst and methanol (MeOH) to produce crude DMT and EG and subjecting the reaction mixture to recrystallization in a MeOH solvent. .

(9) DMT distillation process to purify DMT by distilling MeOH off the DMT cake.

(10) A hydrolysis step of producing TA by hydrolyzing a purified DMT obtained by distillation with water at a temperature of 230 to 250 ° C.

(11) A step of cooling the slurry of TA and water obtained in the hydrolysis step.

(12) The process of obtaining a TA cake by solid-liquid separation operation from the water slurry of cooled TA.

(13) A slurry adjustment step of mixing a TA cake and EG and adjusting the molar ratio of EG / TA to a ratio of 1: 1 to 1: 3.

(14) A step of esterifying TA and EG to obtain a PET oligomer.

(15) Initial melt polycondensation to add polycondensation reaction catalyst and stabilizer to PET oligomer, melt polycondensation reaction at 260-300 ° C. under a low vacuum of 1.3 kPa to 4.0 kPa to remove EG, thereby increasing the degree of polymerization. fair.

(16) A late melt polycondensation step of melting polycondensation at 270 to 300 ° C under high vacuum of 67 Pa to 0.7 kPa to further distill the EG to further increase the degree of polymerization.

(17) Solid phase polymerization process which raises a polymerization degree in order to obtain PET suitable for a bottle.

Hereinafter, the present invention will be described for each step. In addition, in this invention, the process before the process accompanying a chemical reaction from process (1) to process (4) is called a pretreatment process. In this pretreatment step, the PET bottle packing bales collected and collected separately are unpacked, and then iron and aluminum are removed. These metals can be easily removed by using a metal detector. Subsequently, the recovered PET bottle is crushed into 2 to 30 mm squares. The grinding size is more preferably 2 to 20 mm square. By this operation, depolymerization reactivity is improved and the treatment capacity of PET bottle waste is improved. This effect is particularly effective for the thick portion, which is a portion that is crystallized and whitened, in order to increase the strength and dimensional stability of the PET bottle. The pulverized product is often mixed with plastics different from polyesters such as PE, PP, PS, and PVC, which are materials of caps or labels included in the polyester resin as impurities.

In the present invention, reaction conditions are selected so that the phases do not decompose in a later reaction step to reduce the purity of the recovered monomer, but the plastics are attached to the reactor or the eyes of the filter. In the pretreatment process, it is important to smoothly prevent the phase from entering the reaction process by removing the plastics in the pretreatment process, because there is a possibility of undesirably affecting the handling such as clogging. Become.

However, as in the case of carrying out material recycling, the above-described multi-faceted process for completely removing the plastics is not required, and only the minimum required process is required.

In order to remove the thin film (PE, PP, PS, PVC, etc.) used for a label etc. different from polyester from the said grinding | pulverization, a label is first removed by wind power sorting. At this time, if the air volume is too large, it is removed along with the polyester resin as an active ingredient, so it is necessary to adjust the air volume. By this wind sorting, labels mainly composed of PP, PS and PVC can be almost completely removed.

Subsequently, in order to remove the cap containing PE as a main component which cannot be removed in wind sorting, the pulverized product is provided to a specific gravity sorter, and different plastics such as PP and PE having a specific gravity smaller than water are removed by specific gravity sorting. Get flakes

Since the specific gravity sorter also serves as a facility for washing impurities (soft drinks, soy sauce, etc.) derived from edible and the like remaining in the polyester resin, there is no problem even if the contents remain in the resin. The washing water separated by centrifugation is recycled to the specific gravity separator again, and part of it is purged and subjected to drainage treatment. In addition, sand having a significantly higher specific gravity than water and PET is removed by depositing at the bottom of a facility to be washed with water.

The recovered flakes discharged from the specific gravity separator are transported to the reactor of the reaction step via the flake storage tank by air transportation. When the size after grinding in the previous grinding step is defined as being relatively large at an angle of 30 to 150 mm, the transportation efficiency in this air transportation step is deteriorated, or problems such as clogging of the rotary valve occur. It is effective to grind to 2-30 mm each degree.

In the recovered flakes before air transportation, about 0.5% by weight of water used in the centrifugal separation operation by the decanter remains on the basis of the weight of the recovered flakes. These moistures may adversely affect the reaction rate in the depolymerization process, but since they are dried during air transportation, the water content is finally reduced to 0.1% by weight or less based on the weight of the recovered flakes. none.

Although it is possible to remove most components other than polyester in the above pretreatment process, the pretreatment process is completed by much less process than when material recycling is performed. This is because even if impurities remain, for example, the impurities can be separated by physical and chemical separation methods in the next reaction step. In the material recycling, the colored bottle becomes an impurity and must be removed by a sorting machine. However, in the method of the present invention, the pigment contained in the colored bottle can also be removed in a later reaction step, which can be usefully reused as a resource.

Next, the depolymerization catalyst used in step (5) is selected from the group consisting of carbonates, hydrogencarbonates, hydroxides, alkoxides of alkali metals, carbonates, hydrogencarbonates, hydroxides, alkoxides of alkaline earth metals, manganese acetate, and zinc acetate. It is preferable to include at least 1 type of metal compound, and the addition amount shall be 0.1-10 weight% based on the weight of PET flakes provided in process (5). Moreover, it is preferable to make the quantity of EG used at this process (5) into 0.5-20 weight times of the weight of the PET flakes provided at process (5). As reaction conditions, the reaction at the temperature of 175-190 degreeC and the pressure of 0.1-0.5 Mpa is preferable. As a result, BHET is obtained.

In the step (6), the solid foreign matter not dissolved in the reaction solution is subjected to solid-liquid separation.                 

In process (7), the water component in crude BHET by-produced by depolymerization is mainly distilled off. In this step, it is preferable to perform distillation and concentration operation under the pressure of 1.3-133 kPa.

The transesterification catalyst used in the step (8) is at least selected from the group consisting of carbonates, hydrogen carbonates, hydroxides, alkoxides of alkali metals, carbonates, hydrogen carbonates, hydroxides, alkoxides of alkaline earth metals, manganese acetate, and zinc acetate. It is preferable to include 1 type of metal compound, and the addition amount shall be 0.1-10 weight% of the weight of PET flakes provided in the process (5). In addition, the amount of MeOH used in this step (8) is preferably 0.5 to 20 weight times the weight of the PET flakes provided in the step (5), and the reaction under a pressure of 65 to 85 ° C and 0.1 to 0.3 MPa is preferable.

In the step (9), MeOH is mainly distilled off from the obtained DMT cake to purify the DMT.

In the step (10), the amount of water to be supplied is 0.5 to 5 times by weight of the DMT weight, preferably 0.8 to 1.2 times by weight, and the reaction is preferably carried out at a temperature of 230 to 270 ° C.

In the step (11), the aqueous slurry of TA obtained by cooling the reaction product is dehydrated by the solid-liquid separation operation of the step (12), and preferably a water content of about 10 to 20% by weight of water. Separately recover as a TA cake.

In the obtained water-containing TA cake, EG is thrown into slurry so that the molar ratio of TA / EG may be 1: 1-1: 3 in the process (13). The water content in the slurry is preferably in the range of 0.1 to 20% by weight based on the weight of EG.

In place of the above-described step (13), the following steps (13a) to (13b) may be passed and then supplied to the step (14).

Step (13a): A step of treating the TA cake obtained in step (12) with a dryer such as a vibrating fluid tank or an airflow dryer of an inert gas to obtain a powder TA having a water content of 0.5% by weight or less.

Process (13b): The process of inject | pouring the powder TA obtained by the process (13a) into a slurry adjustment tank, inject | pouring EG rules so that the molar ratio of TA / EG may be 1: 1-1: 3, and making it slurry.

However, in the case where the above steps (13a) to (13b) are passed, since the enormous energy consumption for drying the water in the TA cake is accompanied, the method by the method of the step (13) is more preferable.

In addition, TA obtained by the hydrolysis of DMT is preferable because the handling property is improved when the slurry is EG in a state where a small amount of water remains, and the water content in the EG slurry of TA is based on the weight of EG. It is preferable to exist in the range of 0.1 to 20 weight%, Especially preferably, it is 1 to 5 weight%.

In process (14), when esterifying TA and EG and obtaining a PET oligomer, it is preferable to make esterification temperature into 260-270 degreeC. The total content of terephthalate monomethyl (MMT) and DMT is in the range of 1 to 5000 ppm.

In the step (15), the polycondensation reaction catalyst used in the PET oligomer is a catalyst selected from the group consisting of germanium oxide, antimony trioxide and titanium trimellitate titanium compound, which is supplied to the step (13). It is preferable to set it as 0.002-0.1 weight% of TA weight to become. When the polycondensation reaction catalyst used in the step (15) is amorphous germanium dioxide, it is preferable to present 20 to 150 ppm in terms of germanium element on the basis of TA, and when the polycondensation reaction catalyst is antimony trioxide, it is based on TA It is preferable to make 100-400 ppm exist in antimony element conversion, and when a polycondensation reaction catalyst is titanium tetrabutoxide, it is preferable to exist 1-100 ppm in titanium element conversion based on TA, and a polycondensation reaction catalyst In the case of titanium trimellitate, it is preferable to present 1-10 ppm in terms of titanium element on the basis of TA, and when the polycondensation reaction catalyst is a reactant of titanium tetrabutoxide and mono-n-butylphosphate, based on TA 1 to 100 ppm in terms of titanium element is preferably present, and the polycondensation reaction catalyst In the case of a reactant of no-n-butylphosphate, it is preferable to present 1 to 100 ppm in terms of titanium element based on TA, and when the polycondensation reaction catalyst is a reactant of titanium tetrabutoxide and phenylphosphonic acid, TA is It is preferable to present 1-100 ppm in terms of titanium element on the basis, and when the polycondensation reaction catalyst is a reactant of titanium trimellitic acid and phenylphosphonic acid, it is preferable to present 1-100 ppm in terms of titanium element on the basis of TA. Do. Moreover, as a stabilizer to add, phosphoric acid esters, such as trimethyl phosphate, a triethyl phosphate, and a triphenyl phosphate, phosphorous acid esters, such as a triphenyl phosphite and a trisdodecyl phosphite, methyl acid phosphate, dibutyl phosphate, and a monobutyl Preference is given to phosphorus compounds such as phosphate acidic phosphoric acid esters, phosphoric acid, phosphorous acid, hypophosphorous acid and polyphosphoric acid. It is preferable to make reaction conditions into 260-300 degreeC under weak vacuum of 1.3 kPa-4.0 kPa.

In process (16), it is preferable to make reaction conditions into 270-300 degreeC under the high vacuum degree of 67 Pa-0.7 kPa.

In the step (17), the solid phase polymerization reaction in which the degree of polymerization is adjusted to reduce the cyclic oligomer, acetaldehyde, or the like may be performed under nitrogen atmosphere or under vacuum.

This invention is demonstrated further more concretely using FIG. 1 which shows one aspect of the recycling method of the PET bottle of this invention below.

The recovered PET bottle flakes treated by the pretreatment step (not shown) of steps (1) to (5) are supplied from the source (11 in the figure), the depolymerization reaction catalyst is supplied from the supply tank (10 in the figure), and EG is supplied. From the line (10a in the drawing) into the depolymerization tank (1 in the drawing) at the same time, the PET flakes are depolymerized in this depolymerization tank (1 in the drawing).

The depolymerized mixture is sent to a solid-liquid separator (2 in the figure). Components that are not dissolved in the sea bath (1 in the drawing) are separated in the solid-liquid separator (2 in the drawing) and removed out of the system as a solid. Moreover, this solid substance is wash | cleaned again by EG in a washing tank (3 in drawing), and the deposit on the solid surface is circulated-supplied to depolymerization tank (1 in drawing) as needed. In addition, the solid substance itself is separated and removed by the solid substance tank (16b in drawing). Here, the residence time in the depolymerization tank (1 in the drawing) may be 1 to 10 hours, and the internal temperature may be 175 to 190 ° C.

Subsequently, the depolymerization reaction product after depolymerization reaction is sent to a distillation / concentration tank (4 in drawing), and EG is distilled and distilled off so that ratio of EG and depolymerization reactant may be 0.5-2.0 by the weight ratio. EG distilled off can be circulatedly supplied to the depolymerization tank (1 in drawing).

Then, the concentrated depolymerization reactant liquid is supplied to a transesterification tank (5 in the figure), and the transesterification catalyst is supplied from the source (13 in the figure) and MeOH is supplied from the source (12 in the figure), The depolymerization reaction solution is converted to DMT and EG. It is preferable to process the inside temperature of the transesterification reaction tank at the internal pressure of 65-85 degreeC and 0.1-0.3 Mpa by making residence time into 0.5 to 5 hours. The resulting mixture of DMT and EG is cooled with excess MeOH, and this is fed to a solid-liquid separator (6 in the figure) to prepare a cake of DMT and a mixed liquid of EG and MeOH.

Here, since the separated DMT cake contains MeOH as a mother liquid, it is further slurryed by MeOH and solid-liquid separation is carried out again. Moreover, the cake of this DMT is supplied to a DMT distillation column (7 in drawing), and the refined DMT is collect | recovered in a DMT recovery tank (14 in drawing). The remaining liquid at the bottom of the column of this distillation column (7 in the drawing) is returned to the depolymerization tank (1 in the drawing) via a line (7a in the drawing), and the rest is discarded out of the system (18 in the drawing).

On the other hand, the mixed liquid of EG and MeOH separated in solid-liquid separator (6 in figure) is supplied to a MeOH refinery tower (9 in figure), and an EG distillation column (8 in figure), and MeOH and EG are distilled off. This distilled-off MeOH can be used as a part of MeOH supplied to a transesterification tank (5 in drawing). Further, the remaining liquid at the bottom of the column of the MeOH purification column (9 in the drawing) is fed to the EG distillation column (8 in the drawing) to distill off the EG. A part of EG distilled off is used as EG supplied to a depolymerization tank (1 in drawing) via a line (10a in drawing), and the remaining EG is collect | recovered and extracted out of the system (15 in drawing).

In addition, a part of the remaining liquid of the EG distillation column (8 in the drawing) is returned to the depolymerization tank (1 in the drawing), and the rest is discharged out of the system (17 in the drawing) as waste.

Subsequently, a process of obtaining TA by hydrolyzing DMT will be described with reference to FIG. 1.

The purified and accumulated DMT in the recovered DMT bath (14 in the drawing) is heated to the hydrolysis reaction temperature by the DMT heater (19 in the drawing) while being in a molten state. The heated DMT is fed to a hydrolysis reactor (20 in the figure) with the hot water heated in a water boiler (28 in the figure). It is preferable that the weight ratio of water / DMT supplied to the reactor is in the range of 1: 0.5 to 1: 4. It is preferable that the reaction temperature in this reaction tank is 230-250 degreeC, and reaction pressure is 2.9-4.0 Mpa (gauge pressure). The hydrolysis reaction is an equilibrium reaction, and a high reaction rate can be realized by efficiently removing the MeOH produced by the reaction. Thus, as a heat source for rapidly removing MeOH and also maintaining the reaction temperature, high pressure steam generated in a water boiler (28 in the figure) is introduced into the reactor. From the upper part of the reactor, the water accompanying Me0H which is a by-product of the hydrolysis reaction is removed. It is preferable that the weight of the steam introduced from the water boiler and the water extracted from the upper part of the reactor are the same amount. It is preferable that the residence time in a hydrolysis reactor is 1 to 5 hours.

Next, it supplies to the cooling tank (21 in drawing) for cooling the high temperature TA / water slurry obtained in the hydrolysis reaction tank (20 in drawing). Since the cooling tank is accompanied by a sudden pressure change, water in the slurry is evaporated. In order to make up for the shortage of water consumed by the reaction with evaporated water, water is supplied from a water supply tank (29 in the figure). The water to be supplied is preferably pure water ion-exchanged to prevent the incorporation of impurities in the product, and it is also preferable to use dissolved air, especially oxygen-depleted water, to prevent corrosion of the instrument, including hydrolysis reactors. desirable.

The cooled TA / water slurry is fed to a solid-liquid separator (22 in the figure) to separate the TA cake and water. The TA cake obtained by the solid-liquid separator is supplied to a slurry adjustment tank and adjusted to the slurry of 1: 1-1: 3 by the EG supplied from an EG supply source (25 in drawing) by the molar ratio of EG / TA.

Here, the water / MeOH mixed vapor generated from the hydrolysis tank (20 in the figure) is condensed by a steam condenser (26 in the figure), and then distilled into MeOH and water in the MeOH distillation column (27 in the figure), from the top of the tower. MeOH obtained is supplied to the said MeOH refinery tower (9 in the figure), and is distilled again. In addition, water obtained at the bottom of the column of the MeOH distillation column (27 in the drawing) is sent to a water supply tank (23 in the drawing), heated in a water boiler (28 in the drawing), and circulated again to a hydrolysis reaction tank (20 in the drawing). Supplied.

MeOH produced by the hydrolysis reaction becomes dimethyl ether (hereinafter abbreviated as DME) in part by dehydration reaction. This DME is sent from the steam condenser (26 in the figure) to the exhaust gas treatment facility (30 in the figure) as a steam and is burned.

In addition, most of the water separated in the solid-liquid separator (22 in the drawing) is sent to the water supply tank (23 in the drawing) for circulation, and part is sent to the wastewater treatment facility (32 in the drawing) as drainage.

Subsequently, the process of obtaining PET polymer from the obtained TA slurry is demonstrated by FIG.

A TA / EG slurry having a molar ratio adjusted in a TA slurry tank (24 in the figure) is fed to an esterification tank (33 in the figure) and a PET oligomer is obtained by esterification. It is preferable to make reaction temperature of an esterification tank (33 in drawing) into 260-270 degreeC, and the residence time of 1 to 5 hours is preferable.

During this time, the EG / water reaction product mixture is distilled off and separated into EG and water by an EG distillation column (41 in the figure). EG is distilled again in the EG distillation column (not shown in the figure), and again in the EG distillation column (8 in the figure).

The PET oligomer obtained in the esterification tank (33 in drawing) is added to germanium dioxide as a catalyst and trimethyl phosphate as a stabilizer, and is then supplied to an initial polycondensation reaction tank (34 in drawing), and vacuumed by a vacuum apparatus (44 in drawing). Aspirated, and polycondensation reaction is performed on condition of 260-300 degreeC under the weak vacuum of 1.3-4.0 kPa. In addition, the obtained initial polycondensate is supplied to a late polycondensation reaction tank (35 in drawing), and it is vacuum-sucked by the vacuum apparatus (44 in drawing), and performs a polycondensation reaction at 270-300 degreeC under the high vacuum degree of 67 Pa-0.7 kPa. do. The EG by-produced in the polycondensation reaction from the initial polycondensation reactor (34 in the drawing) and the late polycondensation reaction tank (35 in the drawing) are distilled together in the EG distillation column (8 in the drawing) via the EG bath (not shown). do.

The PET polymer obtained in the late polycondensation reaction tank (35 in the drawing) is extracted from the late polycondensation reaction tank (35 in the drawing) in a plate state or strand state, cooled in a cooling water bath (36 in the drawing), and then cutter (in the drawing). 37) into pellets. The obtained PET pellets are subjected to a polycondensation reaction in the form of a solid pellet in order to obtain a degree of polycondensation of a predetermined PET polymer suitable for PET bottles in a solid-state polymerization reactor (38 in the figure) equipped with a dryer and a precrystallizer. This polycondensation reaction may be a reaction under vacuum or a reaction under a nitrogen stream. The final product PET is stored in a reservoir (39 in the figure). This PET polymer is used as a polymer suitable for PET bottles.

In addition, PET oligomers and PET polymer residues generated in the initial polymerization tank, the late polymerization tank, and the solid-phase polymerization tank may be directly supplied to the depolymerization tank for depolymerization reaction, or may be fed to a pulverizer and pulverized and supplied to the depolymerization reactor. Can be reused with as little loss as possible in a series of processes. In addition, by distilling water, EG, and MeOH generated in each step, a substantial portion can be circulated and supplied anywhere in the series of steps, and the loss can be reused as little as possible.

Hereinafter, although an Example demonstrates the content of this invention more concretely, this invention is not limited at all by these. In addition, each value in the Example was calculated | required according to the following method.

1. Analysis of DMT:

(1) Chlorine content in DMT:

DMT was dissolved in MeOH, and the chlorine concentration was determined by a chlorine-sulfur analyzer / total organic halogen analyzer ("TOX100" manufactured by Mitsubishi Chemical Corporation.) On the basis of the chlorine content in the previously obtained mixture.

(2) organic impurities in DMT:

The DMT was subjected to a recrystallization extraction operation using an acetone solvent and a MeOH solvent, and then concentrated, followed by gas chromatography in a special reagent acetone solvent (apparatus: Hewlett-Packard Development Company, LP HP5890, capillary column: J & W DB) -17) was used.

2. Analysis of Terephthalic Acid:

(3) 4-CBA, p-TA:

After terephthalic acid was dissolved in 2N-ammonia water, it was separated and measured by a liquid chromatograph system (LC-6A) manufactured by SHIMADZU CORPORATION, and a STRφDS-H column.

(4) MMT, DMT weight concentration:

Obtained by high performance liquid chromatography (equipment: HPLC D-7000 manufactured by Hitachi, Ltd., packed column: RP-18; two).

(5) BA weight concentration:

After esterification with diazomethane, n-tridecane was used as internal standard and 10% SE-30 was calculated | required by the gas chromatograph used for the separation column.

(6) 250 ℃ heat resistance alkali permeability:

After terephthalic acid was kept at 250 degreeC for 2 hours, it dissolved with 2N potassium hydroxide, and the UV transmittance of wavelength 400nm was measured with the spectrophotometer (equivalent to UVIDEC660 by JASCO Corporation).

3. Analysis of PET:

(7) intrinsic viscosity:

The sample cut out from the chip | tip and the molded object was measured by the usual method, it melt | dissolved in o-chlorophenol in the density | concentration of 0.012 g / mL, and once cooled, the solution was cooled at the temperature condition of 35 degreeC using Oswald viscous tube. It calculated and calculated | required from the measured solution viscosity.

(8) haze:

Nippon Denshoku Industries Co., Ltd., a sample cut out in the size of 50 mm x 50 mm from the bottle body, It measured by the color and color difference meter (MODEL 1001DP) of manufacture.

(9) Acetaldehyde Content:

The acetaldehyde (hereinafter abbreviated as AA) content is freeze-pulverized, put into a vial bottle, held at 150 ° C. for 60 minutes, and then Hitachi, Ltd. It calculated | required using the manufacturing head space gas chromatography.

(10) Diethylene Glycol Content:

The sample was decomposed using catcher hydrazine and determined using gas chromatography ("263-70" manufactured by Hitachi, Ltd.).

(11) Oligomer (cyclic trimer) content:

After the sample was crushed by a grinder, a certain amount was weighed, and once dissolved with a small amount of hexafluoroisopropanone / chloroform mixed solution, it was then diluted with chloroform to a constant concentration (50 g / L). The sample solution was subjected to gel permeation chromatography (GPC, ALC / GPC244 type manufactured by Waters) to isolate the low molecular weight region and detect its peak, based on a calibration curve obtained from a standard sample of a cyclic trimer. The oligomer amount in the sample was measured.

Example 1

Unpacked PET bottle bales (120mm bale with bale dimensions: 900mm × 1000mm × 550mm), which were collected and collected separately, were removed by iron and aluminum by a metal detector and put into the grinder, and the screen diameter of the grinder was reduced to 10mm. It set and grind | pulverized. After that, the pulverized product is provided to a wind sorter, and the label attached to the bottle containing PE, PS, and PP as a main component is removed, and PP and PE are main components while washing and removing the contents of the bottle by washing and gravity separation. Labels not removed by the cap and wind sorting were removed to obtain recovered PET flakes. The recovered PET flakes were transported for storage in a recovered PET flake feed tank by air transport. Next, 100 parts by weight of recovered PET flakes from the recovered PET flake supply tank were supplied with 360 parts by weight of EG from the EG supply line and 2.7 parts by weight of sodium carbonate from the polymerization catalyst supply tank, and held at 180 ° C. for 4 hours and half under stirring. It was.

The depolymerization reaction process liquid by EG was thrown into the filtration apparatus enclosed by the heater which heats the surroundings at 170 degreeC, and is equipped with 100 mesh wire mesh as a filter medium, and the hot-time filtration was performed. The residue on the filter was washed by 90 parts by weight of EG heated to 170 ° C., and the washing liquid was collected in the washing liquid container.

The depolymerization reaction treatment liquid obtained by hot filtration was concentrated by distillation under reduced pressure of 6.65 kPa, and 270 weight part of EG was collect | recovered as distillate.

From this concentrate and the transesterification catalyst tank, 2.7 parts by weight of sodium carbonate and 180 parts by weight of MeOH were added to a transesterification reactor, and the transesterification reaction was carried out by maintaining the liquid temperature at 75 ° C. for 1 hour while stirring. The resulting mixture of DMT, EG and MeOH was cooled to 40 ° C. and a DMT cake was obtained in the continued solid-liquid separator. The DMT cake was once introduced into a MeOH washing tank, 180 parts by weight of MeOH was added thereto, stirred and washed at 40 ° C, and then solid-liquid separation was carried out by a centrifugal separator to obtain a DMT cake. The obtained DMT cake was again put into a MeOH washing tank, and this time, DMT was melt | dissolved at 160 degreeC, and the remaining MeOH was distilled off. The molten DMT was placed in a DMT distillation column, and DMT was distilled off as a distillate by vacuum distillation at a pressure of 6.65 kPa to obtain 83 parts by weight as a recovered DMT. This DMT was sent to a DMT recovery tank.

In this process, the recovered DMT was a high purity DMT whose chlorine concentration was 1 ppm or less and the total amount of organic impurities was 100 ppm or less.

Next, the molten DMT at the rate of 100 parts by weight per hour from the DMT recovery tank, the heating water at a rate of 100 parts by weight per hour from the water boiler, and the high pressure steam from the water boiler at a temperature of 270 ℃, Each was continuously fed to a hydrolysis reactor at a rate of 400 parts by weight / hour. The liquid temperature of the hydrolysis reaction tank was 250 degreeC, It was made to react, ensuring the residence time of 4 hours, stirring, and Me0H produced | generated at that time was distilled off with water vapor from the reactor head part. The distillation discharge rate was about 400 parts by weight / hour as a mixed vapor of water and Me0H, and the internal pressure at this time was about 4 MPa.

The obtained water slurry of TA was sent to the cooling bath at a rate of about 166 parts by weight / hour. The TA / water weight ratio in the slurry in this cooling bath is a weight ratio of about 1/1. The TA / water slurry at a temperature of about 250 ° C. was cooled by latent heat of evaporation of water when flashed at atmospheric pressure, and kept cooled to about 100 ° C. Water equal to the amount of water evaporated at the time of cooling was supplied to the cooling tank, so that the TA / water weight ratio in the slurry in the cooling tank was maintained at a weight ratio of about 1/1.

The TA / water slurry was sent to the solid-liquid separator from this cooling tank at the rate of 166 weight part / hour, and the cake of TA was obtained. The TA / water weight ratio of this water-containing TA cake was about 83:12. The hydrous TA cake was sent to the slurry bath, which is the next process, while wet.

The concentrations of DMT and MMT in the obtained wet TA were 500 ppm and 50 ppm, respectively, and the total content of 4-CBA, p-TA, and BA was 30 ppm. Moreover, 250 degreeC heat-resistant alkali permeability was 99.9% or more, and it was TA suitable as a raw material of PET for bottles.

Subsequently, a slurry composed of 45 parts by weight of TA cake (40 parts by weight of TA and 5 parts by weight of water) and 22 parts by weight of EG was fed to a polycondensation tank, followed by esterification reaction at atmospheric pressure at 275 ° C. for 4 hours. The water which accompanies the water and TA which accompanies TA is made to flow out of the system, and it reacts to 97% of esterification reaction rates, the oligomer of polymerization degree 5-10 is adjusted, and the EG solution of trimethyl phosphoric acid (5.5 in the factor conversion concentration) Molar%) 0.017 parts by weight and EG solution of germanium dioxide (concentration 1.0 mole% in terms of germanium atoms) were added, and polycondensation was carried out for 1 hour under a reduced pressure of 2000 Pa, followed by a reduced pressure of 133 Pa for 2 hours at 277 ° C. It was.                 

The produced polymer was extracted in a strand shape from the outlet formed by directly connecting the cooling water tank to the bottom of the polycondensation tank, cooled in water, and then cut into chips to obtain pellets. The obtained polymer pellet was crystallized in a stirred fluidized crystallizer, dried at 140 ° C. for 3 hours under nitrogen flow, and then transferred to a packed-bed solid state polymerization column, and then polymerized in solid state at 215 ° C. under nitrogen flow for 22 hours to form a chip-like polyethylene tere. Phthalate resin was prepared.

The intrinsic viscosity of the obtained chip was 0.79, AA content was 3.0 ppm, and oligomer content was 0.3 ppm.

Subsequently, the obtained chip was placed in a vacuum dryer and dried at 160 ° C. for 5 hours, and then, using an injection molding machine (“M-100 DM” manufactured by Meiki Co., Ltd.), a cylinder temperature of 275 ° C., a screw rotation speed of 160 rpm, A cylindrical preform having an outer diameter of about 28 mm, an inner diameter of about 19 mm, a length of 136 mm, and a weight of about 56 g was injection molded at a differential pressure time of 3.0 seconds, a mold temperature of 10 ° C, and a cycle of 30 seconds.

The intrinsic viscosity of the obtained preform was 0.68 and 7.5 ppm of AA content, and moldability and external appearance were favorable.

Subsequently, the preform was preheated with an infrared heater so that the surface temperature was about 110 ° C, stretch blow-molded using a blow molding machine set to a blow pressure of 0.5 to 4.0 MPa and a mold temperature of 150 ° C, and the average thickness of the trunk portion was 330 µm, A PET bottle having a volume of about 1.5 liters was obtained. The haze of the obtained PET bottle was 0.6%, and it was confirmed that the present invention makes it possible to recycle the used PET bottle as a PET bottle again.

Example 2

In Example 1, after obtaining a wet TA cake having a TA / water weight ratio of about 83:12 obtained by cooling and solid-liquid separation after the hydrolysis reaction, the cake was placed in a nitrogen stream dryer at a rate of 95 parts by weight / hour. The dump was fed and dried. The moisture content of the dried TA powder was 0.2% by weight. This TA powder was sent to a TA reservoir.

The concentrations of DMT and MMT in the obtained TA powder were 500 ppm and 50 ppm, respectively, and the total content of 4-CBA, p-TA, and BA was 30 ppm. Moreover, 250 degreeC heat-resistant alkali permeability was 99.8% or more, and it was TA suitable as a raw material of PET for bottles.

Next, 83 weight part / hour is injected into a TA slurry tank from a TA storage tank, and EG is charged at a speed | rate of 50 weight part / hour, and it stirs and slurrys. Subsequently, TA / EG slurry was supplied from the TA slurry tank to the esterification tank at the feed rate of 133 weight part / hour, and it stirred, distilling off EG and water so that a residence time might be 2 hours, stirring at reaction temperature 270 degreeC. The distilled EG was reacted while distilling off water with the generated EG in this process. Distilled EG can be used for depolymerization reaction by distillation with the generated EG in this process. The water was drained with other generations. The PET oligomer obtained in the esterification tank was fed to the initial polymerization tank at 102 parts by weight / hour, and the Ge ₂ O ₃ (germanium oxide) catalyst was supplied at a feed rate of 0.015 parts by weight, and stirred under a weak vacuum of 2 kPa, The polycondensation reaction was carried out at 280 degreeC, distilling EG off. The distilled-off EG can be used for depolymerization reaction if it distills together with some other EG.

PET oligomer was supplied to the post-polymerization tank from the initial polymerization tank at a feed rate of 97 parts by weight / hour, stirred in a high vacuum of 0.13 kPa in the post-polymerization tank, and the polycondensation reaction was carried out at 280 ° C while distilling EG off. A polymer was obtained. The intrinsic viscosity of this PET polymer was 0.51. This PET polymer was extracted from the late polymerization tank in a molten state, cooled in a cooling bath, cut into pellets by a cutter, and fed into the solid-state polymerization tank in a pellet state at a feed rate of 96.5 parts by weight / hour. In a packed-bed solid-state polymerization tank having a preliminary crystallizer, the jacket temperature was adjusted so that the pellet temperature at the center of the tank was 210 ° C under vacuum of 0.65 kPa, and the solid-phase polymerization reaction was carried out under the condition that the residence time in the tank was about 8 hours. It was. The intrinsic viscosity of the obtained PET polymer was 0.76, AA content was 3.5 ppm, and oligomer content was 0.3 ppm.

It was an optimal polymer as a polymer for PET bottles. In addition, it was stored at 96.4 parts by weight in a PET storage tank from the solid phase polymerization tank. Subsequently, after drying the obtained chip | tip at 160 degreeC in a vacuum dryer for 5 hours, the cylinder temperature was 275 degreeC, screw rotation speed 160 rpm, and primary pressure using the injection molding machine ("M-100DM" by Meiki Co., Ltd.). A cylindrical preform having an outer diameter of about 28 mm, an inner diameter of about 19 mm, a length of 136 mm, and a weight of about 56 g was injection molded at a time of 3.0 seconds, a mold temperature of 10 ° C, and a cycle of 30 seconds.

The intrinsic viscosity of the obtained preform was 0.67, AA content 12 ppm, and the moldability and appearance were favorable.                 

Subsequently, the preform was preheated by an infrared heater so as to have a surface temperature of about 110 ° C, stretch blow-molded by a blow molding machine set to a blow pressure of 0.5 to 4.0 MPa and a mold temperature of 150 ° C, and the average thickness of the trunk portion was 330 µm, A PET bottle having a volume of about 1.5 liters was obtained. The haze of the obtained PET bottle was 0.5%, and it was confirmed that the present invention makes it possible to recycle the used PET bottle as a PET bottle again.

Comparative Example 1

In Example 1, operation similar to Example 1 was performed except having adjusted the screen diameter of the crusher, and making the size of the flakes after grinding into flakes of an average of 100 mm square. As a result, the transportation efficiency in the air transportation of the flakes after grinding fell, and the electrical load of the blower for transportation rose. In addition, the amount of solids remaining on the wire mesh increased when the solid-liquid separation after the completion of the depolymerization reaction. As a result of analyzing the composition of the solid, the increase compared with Example 1 was PET which is an unreacted substance in a depolymerization process. For this reason, the recovery rate of the product fell.

Comparative Example 2

In Example 1, after unpacking the PET bottle bale, it was put into the grinder and ground by setting the screen diameter of the grinder to 10 mm in the same manner as in Example 1; • Flakes that are simply fragmented as a recovered PET flake, without undergoing specific gravity separation, without washing and removing the contents of the bottle, and without removing the different component plastics by specific gravity separation The same operation was performed except having used.

The recovered DMT was analyzed in the same manner as in Example 1, but in the analysis of organic impurities by gas chromatography, many unidentifiable impurities were detected, and the chlorine concentration in the DMT was 20 ppm, and the obtained DMT was referred to as high purity DMT. I could not.

Moreover, 250 degreeC heat-resistant alkali permeability of TA obtained by hydrolysis was also bad, 93%.

And the haze of the PET bottle manufactured by the method similar to Example 1 was bad at 2.5%. Compared with Example 1, the decrease in intrinsic viscosity was large, there was a decrease in transparency, and the color was pale yellow as a whole and was a quality that cannot be used for PET bottles.

Comparative Example 3

In Example 1, the same operation was performed except having carried out depolymerization reaction temperature at the temperature of 220 degreeC. The recovered DMT was analyzed in the same manner as in Example 1, but the amount of chlorine contained was 15 ppm, and in the analysis of organic impurities in gas chromatography, many impurities were detected, and the DMT obtained here could not be called a high-purity DMT.

Moreover, the 250 degreeC heat-resistant alkali permeability of TA obtained by hydrolysis was also bad (85%).

And the haze of the PET bottle manufactured by the method similar to Example 1 was 2.5%. Compared with Example 1, the decrease in intrinsic viscosity was large, there was a decrease in transparency, and the color was pale yellow as a whole and was a quality that cannot be used for PET bottles.

Comparative Example 4

In Example 1, after the transesterification reaction, the same operation was performed except that recrystallization was not performed. The analysis in the recovered DMT was carried out in the same manner as in Example 1, but the isomer impurities of dimethyl isophthalate (DMI) were 800 ppm.

Subsequently, the intrinsic viscosity of the preform obtained by performing the operation after hydrolysis in the same manner as in Example 1 was 0.66. Moreover, as a result of blow molding similarly to Example 1, the haze of the bottle was 2.0%. At the time of molding, the crystallization rate was lowered, and a bottle having sufficient strength and thermal stability could not be obtained.

Comparative Example 5

In Example 1, the same operation was carried out except that DMT distillation in the DMT recovery step was omitted. The recovered DMT was analyzed in the same manner as in Example 1, but the amount of chlorine contained was 5 ppm, and a large number of impurities which were not identified by gas chromatography were detected, and the obtained DMT was not a high purity DMT. In addition, slight off-flavor was observed in DMT.

Moreover, 250 degreeC heat-resistant alkali permeability of TA obtained by hydrolysis was also bad at 90%.

And the haze of the PET bottle manufactured by the method similar to Example 1 was 2.5%, and was a bad product.                 

Comparative Example 6

In Example 1, the same operation was performed except having made reaction temperature of hydrolysis reaction into 180 degreeC. As a result, the concentrations of MMT and DMT in TA were 1300 ppm and 180 ppm, respectively.

The polymerization process was carried out in the same manner as in Example 1 using the TA, but the reactivity was lowered, and it took longer than usual to reach the target intrinsic viscosity, and the pellet was a pale yellow color as a whole. It was the quality which was not usable for dragon.

Comparative Example 7

In Example 1, the same operation was performed except having set the molar ratio of TA / EG in a slurry adjustment tank to 1: 5. As a result, the DEG content in the obtained pellets was 4.3% by weight and became a pale yellow pellet as a whole. The heat resistance was remarkably lowered, and the quality was unusable for PET bottles.

According to the present invention, from the recovered used PET bottle, terephthalic acid of high purity is obtained via dimethyl terephthalate, and the PET polymer for PET bottle is used as a raw material. It becomes possible to effectively use the PET bottle which becomes a social problem effectively.

Claims (24)

The recycling method of PET bottle which contains a polyethylene terephthalate (PET) as a main component and passes the resin bottle waste which contains a component different from it in order to the process of following (1)-(17). (1) A step of unpacking the PET bottle packing bales collected and collected separately. (2) A grinding step of forming a flake shape of 2 to 30 mm square after removing iron and aluminum from the unpacked PET bottle with a metal detector. (3) Process of separating component polymer different from PET, such as label (thin film) which consists of polyethylene (PE), polystyrene (PS), polyvinyl chloride (PVC), etc. from flake shaped PET bottle piece by wind sorting. (4) Washing foreign substances inside and outside of PET bottle pieces and / or contents residues in PET bottles with water, and removing sandstone and the like having a higher specific gravity than water and PET, and PE having a smaller specific gravity than water. Washing and gravity screening process which separates dissimilar plastics such as PP and PP. (5) Bis-β-hydroxyethylene terephthalate (PET) was injected into ethylene glycol (EG) containing a PET depolymerization catalyst and treated under a temperature of 175 to 190 占 폚 and a pressure of 0.1 to 0.5 MPa. Depolymerization Process to Generate BHET) (6) Solid-liquid separation process which removes the solid foreign material content which does not melt | dissolve in the said reaction solution. (7) A BHET concentration step of distilling and concentrating a solution component that has passed the solid-liquid separation step. (8) The concentrated BHET is transesterified in a transesterification catalyst with methanol (MeOH) to produce crude dimethyl terephthalate (DMT) and EG, and the reaction mixture is subjected to recrystallization in a MeOH solvent. Exchange and recrystallization process. (9) A DMT distillation step of distilling MeOH out of a DMT cake obtained by recrystallization to purify DMT. (10) The hydrolysis step of producing a terephthalic acid (TA) by hydrolyzing the purified DMT obtained by distillation with water at a temperature of 230 to 250 ° C. (11) A step of cooling the slurry of TA and water obtained in the hydrolysis step. (12) The process of obtaining a TA cake by solid-liquid separation operation from the water slurry of cooled TA. (13) A slurry adjusting step of drying the TA cake obtained in step (12) and feeding it to a slurry adjusting tank to adjust the slurry at a ratio of TA / EG in a ratio of 1: 1 to 1: 3. (14) A step of esterifying TA and EG to obtain a PET oligomer. (15) Initial melt polycondensation to add polycondensation reaction catalyst and stabilizer to PET oligomer, melt polycondensation reaction at 260-300 ° C. under a low vacuum of 1.3 kPa to 4.0 kPa to remove EG, thereby increasing the degree of polymerization. fair. (16) A post-melt polycondensation step of melting polycondensation at 270 to 300 ° C. under high vacuum of 67 Pa to 0.7 kPa to distill off EG to further increase the degree of polymerization more than the degree of polymerization in step (15). (17) The solid-phase polymerization process which raises a polymerization degree rather than the polymerization degree of process (16) in order to obtain PET suitable for a bottle. The depolymerization catalyst according to claim 1, wherein the depolymerization catalyst used in the step (5) is made of an alkali metal carbonate, a hydrogen carbonate, a hydroxide, an alkoxide, an alkali metal carbonate, a hydrogen carbonate, a hydroxide, an alkoxide, a manganese acetate, and zinc acetate. At least one compound selected from the group. The recycling method according to claim 1, wherein the amount of the depolymerization catalyst used in the step (5) is 0.1 to 10% by weight of the weight of the recovered PET flake. The transesterification catalyst used in the step (8) is an alkali metal carbonate, hydrogen carbonate, hydroxide, alkoxide, alkaline earth metal carbonate, hydrogen carbonate, hydroxide, alkoxide, manganese acetate or zinc acetate. A recycling method, which is at least one compound selected from the group consisting of. The recycling method according to claim 1, wherein the amount of the transesterification catalyst used in the step (8) is 0.1 to 10% by weight of the weight of the recovered PET flake. The recycling method according to claim 1, wherein in the step (13), the TA cake and EG are mixed without drying the TA cake and adjusted to a ratio of 1: 1 to 1: 3 by the molar ratio of EG / TA. The recycling method according to claim 1, wherein in the step (13), the water content in the EG slurry is in the range of 0.1 to 20% by weight based on the weight of EG. The TA supplied to the step (14) has a total content of 4-carboxybenzaldehyde (4-CBA), methyl paratoluate (p-TA) and benzoic acid (BA) of 30 ppm or less, and further terephthalic acid. The recycling method in which the total content rate of monomethyl (MMT) and DMT is in the range of 1-5000 ppm. The polycondensation reaction catalyst used in the step (15) is at least one compound selected from the group consisting of a germanium compound, an antimony compound and a titanium compound, and as a stabilizer to be added, trimethyl phosphate and tri Phosphate esters such as ethyl phosphate and triphenyl phosphate, phosphorous esters such as triphenyl phosphite and trisdodecyl phosphite, methyl acid phosphate, dibutyl phosphate, monobutyl phosphate acidic phosphate ester, phosphoric acid, phosphorous acid, hypophosphorous acid, A recycling method, which is at least one compound selected from phosphorus compounds such as polyphosphoric acid. The recycling method according to claim 1, wherein the addition amount of the polycondensation reaction catalyst used in the step (15) is 0.002 to 0.1% by weight of the TA weight supplied to the step (14). The recycling method according to claim 9, wherein the polycondensation reaction catalyst is amorphous germanium, having 20 to 150 ppm in terms of germanium element based on TA. The recycling method according to claim 9, wherein the polycondensation reaction catalyst is antimony trioxide and is present in an amount of 100 to 400 ppm in terms of antimony element based on TA. The recycling method according to claim 9, wherein the polycondensation reaction catalyst is titanium tetrabutoxide, having 1 to 100 ppm in terms of titanium element, based on TA. 10. The recycling method according to claim 9, wherein the polycondensation reaction catalyst is present as titanium trimellitate in the amount of 1 to 10 ppm in terms of titanium element based on TA. The recycling method according to claim 9, wherein the polycondensation reaction catalyst is present as a reactant of titanium tetrabutoxide and mono-n-butylphosphate in the range of 1 to 100 ppm in terms of titanium element based on TA. The recycling method according to claim 9, wherein the polycondensation reaction catalyst is a reactant of titanium trimellitic acid and mono-n-butyl phosphate, and is present in an amount of 1 to 100 ppm in terms of titanium element based on TA. The recycling method according to claim 9, wherein the polycondensation reaction catalyst is present as a reactant of titanium tetrabutoxide and phenylphosphonic acid in the amount of 1 to 100 ppm in terms of titanium element based on TA. The recycling method according to claim 9, wherein the polycondensation reaction catalyst is a reactant of titanium trimellitic acid and phenylphosphonic acid and is present in an amount of 1 to 100 ppm in terms of titanium element based on TA. delete delete delete delete delete delete

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